Use of fluorescence techniques often involves a direct correlation between a fluorophore concentration and fluorometric response (i.e., as the fluorophore concentration increases, so does the fluorometric response). When measuring fluorescence in liquid solutions (e.g., aqueous liquids), relatively high light absorbance and/or turbidity of the liquid solution can prevent obtaining a direct correlation as set forth above, thereby complicating or altogether preventing the use of traditional fluorometric techniques to measure fluorometric response in practical applications. Particularly in cases of relatively high levels of light absorbance from a fluorophore (e.g., greater than about 0.4 absorbance units combined total for excitation and emission lightpaths when using a 1 cm pathlength cell), fluorometric response can even decrease as fluorophore concentration increases, which can occur whether the fluorophore is the only source of light absorbance or whether overall light absorbance is due to the fluorophore and other substances present in the relevant sample. A decrease in fluorometric response as fluorophore concentration increases is an undesirable result for practical applications.
The impact of light absorbance on fluorometric intensity (an example of a fluorometric response) can be predicted using Equation 1 below:% total fluorometric intensity=[(10−0.5*L1*Aex)*100]*[(10−0.5*L2*Aem)*100]  Eq. 1wherein L1=the width across a sample chamber (e.g., a cylindrical flow cell) in the direction that the light is being shone; L2=the width across the sample chamber in the direction of fluorometric response toward a fluorometric detector; Aex=light absorbance at 1 cm of pathlength of a sample at an excitation wavelength(s); and Aem=light absorbance at 1 cm of pathlength of a sample at an emission wavelength(s). Equation 1 assumes that the fluorometric response originates at the center of the sample chamber.
Generally, aqueous liquids utilized in downhole applications are treated with any of several treatment formulations. Aqueous liquids utilized in downhole applications are generally relatively turbid (e.g., from about 100 NTU to about 130,000 NTU) and have relatively high light absorbance, making them less than ideal candidates for fluorometrically measuring the concentrations of certain compositions present therein. Historically, such treatment formulations (e.g., corrosion inhibitor formulation and/or kinetic hydrate inhibitor formulation) have been difficult if not impossible to measure their concentrations and/or control their dosages via traditional fluorometric techniques.